https://www.ecommprofessionals.com/monitoring_ads_to_reduce_acos.html
In Amazon Pay-per-Click advertising, Advertising Cost of Sales (ACoS) is very important. Target ACoS is a measure of success, a volatile percentage and a decisive factor in bidding on search terms. Being an Amazon seller, you must have understood by now, how important a low ACoS is for the success of your Amazon Sponsored Products ads. You may be selling a lot of products, but if your ACoS is very high, it will eat away at your profits.